Field of the Invention
The technical field relates to a DC (direct current) bias circuit, and more particularly to a DC bias circuit used to stabilize alternating current signals output from a mixer circuit of a radio frequency receiver circuit.
Description of the Related Art
FIG. 1 is a block diagram of a radio frequency receiver circuit 10. The radio frequency receiver circuit 10 comprises a low noise amplifier 101, a mixer circuit 102, and an amplifier circuit 103. The radio frequency receiver circuit 10 receives a plurality of radio frequency signals from an antenna 11 and processes the radio frequency signals, wherein the radio frequency signals are high-frequency electromagnetic signals spread on some specific frequency bands, for example, 5 GHz or 2.4 GHz. The low noise amplifier 101 is used to process the received radio frequency signals. The mixer circuit 102 is also called a downconverter and is used to perform a down-conversion operation on the signals processed by the low noise amplifier 101. Finally, the amplifier circuit 103 receives a plurality of alternating current signals output from the mixer circuit 102 and outputs a plurality of corresponding alternating voltage signals. In FIG. 1, the low noise amplifier 101, the mixer circuit 102, and the amplifier circuit 103 can be implemented by analog circuits. In an analog circuit design, variations in the semiconductor process have always been an important issue. This is because variations in the semiconductor process can affect the accuracy of the design parameters of the analog circuits.